1. Technical Field
The invention relates to tire building equipment and in particular to the tire building drum and to the bead setter associated therewith. More particularly, the invention relates to an improved magnetic tire bead setter, a plurality of which are mounted on a bead setter ring which is attached to the bladder push cone of the tire building drum for transporting a tire bead from a load station to a position which is coaxial and radially aligned with the bead locks of the tire building drum.
2. Background Information
In the building of pneumatic tires, various sheets or strip components thereof are laid and placed around a cylindrical drum to build-up the carcass. One of the steps in the tire manufacturing process is the telescopic mounting of a bead ring over the drum around the ends of the tire carcass, which ends are subsequently turned up by an inflatable bladder for forming the usual toroidal shape of the final tire. Prior to the inflation of the turn-up bladders, a plurality of circularly arranged bead lock segments which are mounted on the drum, are expanded radially outwardly by pressurized air, mechanical linkage or other mechanism for positioning the bead ring with respect to the tire carcass.
It is necessary that the bead ring be accurately placed with respect to the bead lock segments to ensure proper positioning of the bead with respect to the tire carcass. Various types of mechanisms, commonly referred to as bead setters, are used with tire building drums for automatically moving a tire bead from a load position axially along the tire building drum to the proper radially aligned position with the bead lock segments. Many of these bead setters include fixed magnets mounted on a bead carrier ring, which in turn is mounted on or formed as a part of the push ring cone of the tire building equipment.
Prior art examples of bead setters having both magnetic and non-magnetic carriers thereon are shown in the following patents.
U.S. Pat. No. 3,839,115 shows a bead setter which includes electromagnetic pole members which hold a bead during the setting operation and a supporting carriage which retracts when the bead is placed on the drum.
U.S. Pat. No. 4,190,482 shows a tire building apparatus having bead setting means which includes magnets that hold the bead rings until they have been placed, afterwhich the holder segments are moved radially outwardly.
U.S. Pat. No. 4,264,387 shows a bead setting device which has magnets with movable segments. However, the segments are not pivotally and slidably mounted on a carrier as the present invention.
U.S. Pat. No. 4,964,931 discloses a bead setter having a frame with a plurality of magnetic segments mounted thereon. Again, the magnetic segments are not pivotally slidably mounted as in the present invention.
U.S. Pat. No. 5,073,225 shows a bead setter having both permanent and electromagnets carried thereon for carrying the bead ring to an install position.
Although many of these prior art bead setters, both magnetic and non-magnetic, perform satisfactorily for their intended purpose, the use of magnetic bead setters is desirable for many applications due to their simplicity. However, certain fixed magnetic bead setters create problems when delivering certain types of tire beads, and in particular beads that have a hexagonal cross section. It is difficult to securely grip these hexagonal beads and orient them in the proper position, yet enable the magnetic carrier ring to have a sufficiently large inner diameter which will clear the diameter developed when the carcass plies, which have been applied over the drum, are expanded outwardly by the bead locks. This outward expansion of the plies is necessary to grip the bead ring, afterwhich the bead setter carrier ring must move axially to a retracted position prior to inflation of the bead turnup bladder.
Thus, the need exists for an improved magnetic bead setter which is able to magnetically grasp and securely support a bead ring thereon even when the bead has different cross-sectional configurations, and accurately position the ring in an outwardly radially aligned position with respect to the expandable bead locks of a tire building drum, and most importantly be able to move axially to a retracted position and clear the carcass ply material previously placed on the drum, after the ply material has been moved radially outwardly by the bead locks.